I got 1 sheet of Yupo to try it for Pt/Pd printing. I was able to coat it even it did absorb only about half the volume most papers would absorb. But almost no image was formed.
There was a very faint image printing out and most of it disappeared during development. I found it interesting as Yupo is made from polypropylene and lacks any polar groups (in contrast to cellulose). So paper (and sizing?) is not an inert substrate but part of the chemistry of image formation.
Jakobb, to my knowing, Yupo isn't suitable for pt/pd or any other iron process w/o priming it with something - that will hold the emulsion - beforehand. (Said that, I don't know anyone doing pt/pd on Yupo BTW...) You can directly print on Yupo with tempera or casein processes, both colloid-dichromate processes which have quite strong and sticky binders... The problem you experienced isn't chemical (the paper is inert to the chemistry of pt/pd) at all, it's a 100% physical problem - the paper just didn't hold the emulsion / image.
I have tried some more papers.
The Strathmore 500 bristol 1ply I got was very alkaline and pretreatment with citric or oxalic acid ruined the smooth surface but still did not give a decent print.
Ruscombe Herschel is much harder than Buxton but has significant more surface structure which is quite distracting. A smooth plate version would be very interesting especially for smaller prints.
One Paper which is quite promising is Zerkall book smooth white. It is slightly alkaline but seem to work with some oxalic acid added to the ferric oxalate. It might be the second best to Buxton in tonality but because of its smoother surface the print are much sharper.
After wet processing Herschel does get quite a strong texture, but this can be dealt with by using a heat press. I give finished prints 8 minutes between two sheets of conservation board, followed by 8 minutes with the face of the print directly against the steel. This leaves the paper much smoother - with less texture than the unprocessed paper actually.
Originally Posted by jakobb